Actin is highly conserved across all eukaryotes, and misregulation by alterations in actin binding protein activity results in severe developmental defects and contributes to diseases such as cardiovascular diseases and cancer. The activities of the >100 known actin binding proteins are well studied; but the signaling pathways and mechanisms that coordinate the functions of multiple actin binding proteins to drive actin remodeling necessary for morphogenesis remain poorly understood. To uncover mechanisms coordinating the activities of actin binding proteins, we take advantage of the powerful genetics and well-characterized, actin-dependent process of follicle or egg development in Drosophila. We have made the novel finding that a class of lipid signals termed prostaglandins (PGs) regulates multiple actin remodeling events necessary for Drosophila follicle development. Our long term goal is to determine the means by which specific PG signaling cascades coordinately regulate particular actin binding proteins to control cytoskeletal dynamics. The critical next step towards achieving this goal are to identify the actin binding proteins acting downstream of PG signaling, elucidate the molecular mechanisms of this PG regulation, and determine how the activities of these actin regulators are integrated. The central hypothesis of the proposed work is that distinct PG signaling cascades regulate specific actin binding proteins to restrict actin filament formation, promote bundle formation, and mediate cortical actin contraction necessary for morphogenesis. Aim 1 will define the specific PG signaling cascade that inhibits inappropriate actin filament formation, and the molecular mechanisms by which it regulate the actin elongation factor Enabled. Additional actin binding proteins regulated by this PG signaling pathway to coordinate actin filament formation with developmental stage will be identified. Aim 2 will delineate a different PG signaling pathway that promotes parallel bundle formation, and the means by which this pathway coordinates the opposing action of two actin binding proteins, Enabled and Capping Protein (a barbed end capper). Aim 3 will uncover the PG pathway that regulates cortical actin contraction by regulating Non-Muscle Myosin Regulatory Light Chain. The expected contributions of this study are the identification of specific PG signaling pathways that inhibit or promote actin filament formation and drive acto-myosin contraction, elucidation of the molecular means by which these pathways regulate four conserved actin binding proteins, and identification of the complement of actin binding proteins that are coordinately regulated by these PG pathways. The contributions of this study will be significant because: 1) it will establis a framework to define the roles of other lipid signals during development; 2) it will provide new insight into the roles of individual PGs in tissue morphogenesis; and 3) it will bring together separate fields - lipid, actin cytoskeletal, and developmental biology. Furthermore, these findings should be broadly applicable to other PG-dependent processes, including cell migration, vertebrate gastrulation, cardiovascular function and disease, and cancer.